Advice on adding closed cooling to 5.7 GSi

[moonshn]

Howdy everyone! I hope the summer is treating you all well so far.

After finding water in the cylinders and pulling heads to find quite a bit of corrosion in a motor with close to 1,000 hours we have decided to go ahead and replace the motor with a rebuilt stroker and new heads while i've got her taken apart.

Boo!

Does anyone know of any resources to look at or opinions to share to help decide if adding a closed cooling system would be worth the effort and cost when the new motor goes in? While this is primarily a fresh-water boat it would be nice to have the option to run in saltwater with a little less worry about corrosion.

My thought process is that a closed system gets me a few benefits:

• Less corrosion in the block and heads even running in fresh-water.
• Easier winterizing.
• Ability to use in saltwater with less detrimental effects.
• Ability to run at operating temps closer to what the 350 was designed for.

Another question though: is there a "full" closed system (including the exhaust manifolds) available for an older Volvo 5.7? All i've seen online so far are "half" systems.

Are there any other pitfalls the more experienced members out there could bring to my attention before i get started down this rabbit hole?

As always, i greatly appreciate everyone who is willing to share their knowledge here.

Cheers!

 

[GeorgeDes]

I’ve got that very same engine on my FW 246 Sundowner and have thought about doing this as well. Like you all I have seen advertised are the half systems that would only circulate fresh water through the block.

 

[Scott Danforth]

You can add a full system or a half system to any new motor. VP only offered half systems from the factory until the cat motors

You would need a bigger separator tank with a full system. The later MOAS separator would work as that was designed for both half and full systems. (And yes, the accronym is Mother Of All Separators)

 

[Scott Danforth]

I’ve got that very same engine on my FW 246 Sundowner and have thought about doing this as well. Like you all I have seen advertised are the half systems that would only circulate fresh water through the block.

only add HX cooling to new motors

 

[Lou C]

I'm interested in this as well. Not for my current engine obviously but when I re-power with re-man or new. I'm in 100% salt water so the ability to cool the exhaust manifolds with antifreeze will save replacing them every 5-7 years so some of the cost of the system will be paid back and then there is longer engine life and easier winterizing. No more groping around in the bilge to get the drain plugs out every fall.

Question:
I wonder if Volvo never offered the full closed system before, because they may have been concerned that the impeller might not have been able to flow enough raw water to keep a bigger heat exchanger cool enough?

Also:
I was looking around on the Mr.Cool website; what I found was interesting. The offer full and half systems for Merc. They offer full and half for OMC Cobra (this surprised me, I e-mailed them to make sure this was not a mistake), but only half for Volvo.

I guess there is a min flow volume that you need for cooling the engine + exhaust manifolds, I recall hearing 30 gpm, or something like that.

The other issue is if you go with a full system, then the exhaust has to be replumbed in that the raw water from the exchanger has to exit via the elbows and the manifolds are fed AF from the thermostat housing and then the coolant loops back to the exchanger. The Volvo style manifold are drilled for fittings on both the front and rear ends, I know the elbows have plugs in them but not sure if they go into the cooling passage....I have the same style on my engine now....

 

[Scott Danforth]

Lou,

you need the AF to exit the manifolds at the top to prevent an air bubble which would cause the manifold to crack

many VP manifolds do not have this option (hence the half system)

so if you have manifolds with a top water port, you can plumb as a full-system

I suggest aftermarket aluminum manifolds if you go with a full system. then get stainless elbows

 

[GeorgeDes]

Sounds like something that may be worthwhile to consider on a newer engine. Mine has 850 hours or so (1999 5.7GSI) and manifolds, risers and heads are about 3 years old and had been fresh water until last year when I started boating in a brackish area. It gets flushed every every outing now as the boat is racked. Hopefully, I’ll be heading north where it will be strictly fresh water again. Based on the expense and time left with this boat, think I can do without the closed system until I buy a newer boat.

 

[Lou C]

Lou,

you need the AF to exit the manifolds at the top to prevent an air bubble which would cause the manifold to crack

many VP manifolds do not have this option (hence the half system)

so if you have manifolds with a top water port, you can plumb as a full-system

I suggest aftermarket aluminum manifolds if you go with a full system. then get stainless elbows

Thanks Scott I was not aware of the differences between the Merc style manifolds and the Volvo style. I can see what you are saying as the Volvo style just has tapped openings front and rear, not front and top. I would still install even a half system since the benefits are still worth it.

 

[moonshn]

Lou,

you need the AF to exit the manifolds at the top to prevent an air bubble which would cause the manifold to crack

many VP manifolds do not have this option (hence the half system)

so if you have manifolds with a top water port, you can plumb as a full-system

I suggest aftermarket aluminum manifolds if you go with a full system. then get stainless elbows

Do you know of anyone selling these? I'm not having much luck finding any.

Thanks for your time also!

 

[Lou C]

Keep in mind with a marine exhaust system, everything has to line up. So you'd have to find a local marine exhaust shop and see if they would lend you a manifold and elbow to see if it will all fit with your exhaust hoses and the aluminum exhaust pipes that connect to the Y pipe. There is the height and the down angle of the elbows to consider as well as how far back they extend. For example, Volvo used to use a 10* down angle, but Merc uses a 5*, 15* and 0* on some models. So it can be tought to adapt something to what you have, unless someone has already done it. I like the Merc dry joint design, if these could be adapted to my OMC engine I would do it next time but I'd have to find a shop that would let me borrow the parts to check fitment.

 

[Scott Danforth]

I would run stainless marine manifolds and have the elbow custom made